1. Field of the Invention
The present invention relates to a process for control of an internal combustion engine. The present invention relates more particularly to control of an internal combustion engine of an agricultural tractor.
2. Discussion of the background
It is known that two separate accelerators for controlling the engine load can be made available to the operator of an agricultural tractor, a first accelerator in the form of a pedal and a second accelerator in the form of a throttle lever. The accelerator pedal is usually returned automatically to idle position by a restoring spring, whereas the throttle lever is not provided with any mechanism for automatic return to idle position.
The position of these two separate accelerators is transmitted to an electronic device for monitoring the power delivered by the engine, which device then controls the engine as a function of the larger of the two signals. The electronic control box then acts directly on the quantity of fuel injected by control signal to the injectors or else to the fuel pump.
This arrangement has the disadvantage that it cannot respond to the action of the operator on the vehicle brake control or controls in such a way that the power delivered by the engine is reduced, canceled out or made negative, (engine brake), independently of the position of the accelerators, as soon as the operator applies the brakes.
The object of the present invention is therefore to remedy these disadvantages by providing an engine control process which takes into account both the action of the operator on the brakes and the position of the accelerators.
By virtue of this invention, in the example of braking on the highway at high speed when the operator has neglected to return the throttle lever to idle position, the brakes will no longer have to work against the propulsive power delivered by the engine. The result is therefore more effective braking, a shorter stopping distance, less heating of the brakes and therefore reduced wear thereof.
The process according to the invention for control of an internal combustion engine provided in a vehicle and cooperating with a throttle lever and an accelerator pedal operates on the principle of determining the quantity of fuel to be injected.
According to the invention, the process is characterized in that the quantity of fuel determined by the respective positions of the accelerator pedal and throttle lever is corrected as a function of the position of the brake pedal of the vehicle.
According to another characteristic of the process according to the invention for control of an internal combustion engine, depressing the brake pedal leads to limitation of the fuel supply to the point that the engine speed reaches the slow speed regardless of the respective positions of the accelerator pedal and throttle lever.
According to another characteristic of the process according to the invention for control of an internal combustion engine, the limitation of fuel supply is maintained for as long as the brake pedal is actuated.
According to another characteristic of the process according to the invention for control of an internal combustion engine, the depression of the brake pedal is taken into account only when the vehicle speed exceeds a given threshold speed.
According to another characteristic of the process according to the invention for control of an internal combustion engine, the limitation of fuel supply is maintained as long as the brake pedal is actuated and as long as the vehicle speed remains greater than the given threshold speed.
According to another characteristic of the process according to the invention for control of an internal combustion engine, when the vehicle speed exceeds the given threshold speed at the start of braking, the limitation of fuel supply is maintained as long as the brake pedal is actuated even when the vehicle speed drops below the said threshold speed.
According to another characteristic of the process according to the invention for control of an internal combustion engine, engine control by the throttle lever is disabled once the brake pedal has been depressed, and the engine is then controlled exclusively by the accelerator pedal, this situation being maintained until the operator returns the throttle lever to idle position.